Electric signaling apparatus



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M. MARTIN. ELEGTRIG SIGNALING APPARATUS No. 454,973. Patented June 30-,1891-.

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M. MARTIN. ELECTRIC SIGNALING APPARATUS No. 454,973. Patented June'30,1891.

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UNITED STATES PATENT OFFICE;

MORRIS MARTIN, OF M ALDEN, ASSIGN OR TO FREDERICK P. FISH, Oi!CAMBRIDGE, MASSACHUSETTS.

ELECTRIC SIGNALING APPARATUS.

SPECIFICATION forming part of Letters Patent No. 454,973, dated June 30,1891. Application filed November 5, 1888. Serial No. 289,961- (Nomodel.)

To all whom it may concern:

'Be it known that I, MORRIS MARTIN, 0 7

Malden, county of Middlesex, and State of Massachusetts, have inventedan Improvement in Electric Signaling Apparatus, of which the followingdescription, in connection with the accompanying drawings, is aspecification, like letters and figures on the drawings representinglike parts.

My invention relates to an electric signaling apparatus, and is shown asemployed for the transmission of fire-alarms automatically, although thesame apparatus might be employed for transmitting other information, andmight be operated by hand or otherwise, instead of automatically by arise in temperature.

The apparatus comprises a signal-transmitter connected in circuit with asignal-receiving station and controlled as to its operation by a localcircuit, the invention consisting mainly in novel features ofconstruction of the said transmitting apparatus and in combinations andarrangements of the parts of said apparatus with the main circuit,connecting it with the signal-receiving station and with the localcircuit by which it is controlled.

For convenience in description the apparatus will be regarded asintended for automatically transmitting an alarm when a fire breaks out,this being the use to which the apparatus is generally put, and therewill be a transmitter at each building or group of buildings to beprotected, which transmitter,

when operated, will send a signal to a main or receiving station, whichsignal indicates the locality of the transmitter, like the usualfire-alarm or district signal-receiving apparatus. The said transmitteris controlled in its operation by one or more local circuits extendingthrough the building or group of buildings to be protected, and soarranged that when the transmitter is set in operation by the properchange in any of said local circuits it transmits not only the signalindicating the general locality, but also an additional signalindicating the-particular part of the building or group of buildings inwhich the fire has occurred, or the change in the local circuit has beenotherwise produced that sets the transmitter in operation.

tent for said break-wheel controlled by the local circuit, incombination with another signaling device, which is the same in effectas and maybe regarded as a set of. simultaneously-moving break-wheels,which device or set of break-wheels is actuated by the same motor as themain break-wheel, but is controlled by a separate detent and soconnected with the motor that the main breakwheel may move independentlyof the said connected set of break-wheels or drum if the detent for themain break-wheel alone is operated, but will accompany the said mainbreak-wheel in a greater or less portion of its movement it both detentsare operated simultaneously. The detent of the main breakwheel isarranged to be operated by a defect in the local circuit other than anactual rupture of the same-such, for example, as a weakening of thebattery or grounding of the local circuit at any pointwhile both detentscuit is actually broken at any point, so that the main locality-signalis transmitted alone if there is a defect in the local circuit; but bothmain and local circuits are transmitted if the local circuit isruptured, as occurs upon the breaking out of a fire.

Figure l is a front elevation of a transmitting-instrument forming partof a signaling apparatus embodying thisinvention; Figs. 2, 3, and t,details to be referred to; Fig. 5, a modification to be referred to;Fig. 6, a diagram showing the circuits and the relations of the variousparts of the apparatus thereto, and Fig. 7 a detail illustratingathermostatic circuit-breaker that may be employed in the local circuit.

The transmitting-instrument represented in Fig. 1, which constitutes oneof the main novel features of the invention, comprises a clock-work ormotor a, which may be such as commonly employed in fire alarmsignalboxes, the actuating-spring of said motor being normally wound up, sothat the motor tends to rotate the shaft 1), except when such rotationis positively prevented by the detent, which will be hereinafterdescribed. The said shaft 1) has fixed upon it a breakwheel orsignaling-surface Z), the specific construction of which is best shownin Fig. 2, and will be described later on, it being sufficient for thepresent to understand that the said break-wheel controls a main circuitand effects the transmission of a signal therein as does the brealowheelof the well-known firealarm and district signaling-boxes. The saidbreak-wheel Z) and the shaft 1) and motor a are normally arrested andretained inopera tiveby a detent, which may be of any usualconstruction, being shown as consisting of a lever 0, one arm of whichengages a projection 0 on the break-wheel I), and the other arm of whichis controlled by the armaturelever (Z of an electro-magnet (Z in suchmanner that said lever c is retained in engagement with the other detentmember 0 as long as the armature remains attracted, but is released whenthe said armature is retracted by the demagnetization or weakening ofthe magnet 61', the said armature being provided with a strong retractor(shown as a counter-weight) (1 which will retract the armature beforethe magnet d is wholly demagnetized, and will thus be operatedbyareduction of the current in said magnet below the amount required forthe safe or normal operation of the apparatus without the totalinterruption of the said current. The shaft 7) also has loose upon it adrum 6, (shown in end elevation in Fig. 3,) composed of insulatingmaterial provided with strips 6 e 860., of conducting materialco-operating with springs 2 &c., which rest against the surface of saiddrum, so that in the rotation of the said drum the said pairs of springswill be alternately connected and disconnected, or the circuit from oneto the other of a given pair of springs will be alternately broken andclosed, as in the operation of an ordinary breakwheel. The said strips 66 &c., are of different lengths, one only co-operating with the pair ofsprings f, while two of them co-operate with the pair of springs f andthree with the pair of springs f and four with the pair of springs f sothat said drum is the same in efiect as a number ofmechanically-connected break-wheels having different numbers of teeth orprojections, the one co-operatin g with the pairof springs f, forexample, having one tooth, the one with the pair f two teeth, the onewith the pairf three teeth, and so on; but this portion of the apparatuswill for convenience be hereinafter spoken of as the drum or localsignaling device, as the different break-wheels or signaling-surfaces ofwhich it is composed indicate the different parts of the locality whichis characterized by the one main signal produced by the break-wheel Z).

There is a connecting medium between the break-wheel I) and drum e,which may consist merely of a projection g on the drum and thecorresponding projection g on the breakwheel, the former being normallyplaced just behind the latter, so as to admit of practically onecomplete rotation of the break-wheel 1') before it engages the drum andtends to turn the latter positively with it. If desired, the saidengaging device g 9' may be constructed, as shown in Fig. 5, so as topermit two or more complete rotations of the break-wheel before the drumis positively engaged by it, and in either case the friction of thesprings f f &c., alone or in connection with an additional frictiondevice will be sufficient to overcome the friction between the drum eand shaft 1) and prevent the rotation of the former until positivelyengaged by the break-wheel b, to which the power of the motoraisdirectly applied. The drum e is also provided witha detent, which mayconsist of a lever 7L, one arm of which engages a projection 71, on thedrum and the other arm of which has a lateral projection 7'0 that isengaged by a proj ection i (see Fig. 4:) on the armature-lever i of anelectro-magnet 1', arranged to retain the detent h h in engagement whilesaid armature is attracted, but to disengage the said detent when thesaid armature is once retracted, and thereafter to permit thefreerotation of the drum 6, whatever may be the position of thearmature-lever 1 The construction of this detent is substantially likethat of the detent c 0 (Z of the main breakwheel, the engagingprojections on the armature-lever and detent-lever being so arrangedthat when the armature is retracted the projection on the detent-leverpasses wholly by that on the armature-lever, as will be readilyunderstood from Fig. 4, thus leaving the detent wholly disengaged andalso leaving the armature-lever free to vibrate under the influence ofits magnet.

The magnet t" is in the same circuit as the magnet (l, but has a weakerretractor and is in a different portion of said circuit, as will behereinafter described, so that the weakening of the current or groundingof the circuit that will cause the release of the armature of the magnet(1 will not release the armature of the magnet i, and consequently sucha weakening of the current orgrounding of the circuit will cause therelease of the break wheel I), but not of the drum e, and under suchcircumstances the break wheel I) will rotate one or more times untilarrested by the engagement of the parts g g, and then further movementof the said break-wheel and of the motor a will be prevented by thedetent h h for the drum, but will take place when the said drum-detentis disengaged. If, however, both detents areoperated simultaneously, asby a complete rupture of the circuit through the magnets d and i, thebreakwheel I) will be operated by the motor, as before, for one or moreturns, while the drum is held stationary by the friction device beforeIIO mentioned, but as soon as the parts g g engage; the drum will becaused to rotate with the break-wheel and both will continue to turntogether until-the motor runs down.

The object of the construction thus far described and the mode ofoperation of the devices in the entire apparatus will be best understoodby referring to the diagram, Fig. 6.

The main circuit connecting the transmitter apparatus thus far describedwith the signal receiving apparatus at the main or signal receivingstation is shown as of substantially the same character as that shownand described in Patent No. 341,115, dated May 4, 1886, which may bereferred to for a fuller explanation of the various arrangements whichwill now be briefly described. The said main line has both terminalsgrounded at the main office, and includes two independentreceiving-instrunients R R, of usual construction, one near eachterminal, and also has near each terminal batteries B B of unequalamount and set, with like poles to line, so that their currents normallyoppose one another, leaving, however, asufficient amount of current onthe line to show whether or not the said line: is unbroken byinstruments which are not shown and need not be de-' scribed, as theyform no part of the present invention.

The main line may be traced as follows: Starting from the ground at 2 atthe receiving-station, it passes through one battery B andreceiving-instrument R, and thence, as shown at 3, to the transmittingapparatus of the first out-station, where the-circuitis normallycompleted, through the break-wheel b "to the portion 4 of the main line,leading onto the next station, and finally returning to the main ofiiceand passing through the receiver R and battery 13 to the ground at 5,making practicallya metallic circuit,but with aground connection at thereceiving-station between the two batteries B and B, so that a groundconnection at any outside point will make two complete independentground-circuits, one through the battery B and instrument R and theother through the battery B and instrument R. The signals aretransmitted by first grounding one side of the line at thetransmitting-station and opening and closing the said grounded circuitand then repeating the same operation upon the line at the oth er sideof the transmitter, so that if the line is in working condition thesignal will first be received on one instrument, as R,ran'd then on theother instrument, as R; but if the line at either side of thetransmitter is broken or grounded the signal'will still be. properlyreceived by the instrument in the other side of the line. Theconstruction of the break-wheel b for eifecting this result is bestshown in Fig. 2. The said break-wheel consists, practically, of half adisk, which is again divided into two parts, or is, in other words, madethick enough in the direction parallel with its axis of rotation toco-operate the springs It 7t are in contact with it, the

said springs constituting the terminals of the parts 3 and 4 of the mainline at either side of said break-wheel, as shown in Fig. 6, so that themain line is normally closed or completed through the said break-wheel,as before stated. The springs m and m are each connectedwith the ground,as shown in Fig. 6, and so arranged that neither of them touch thebreak-wheel when arrested in the normal position, the said wheel beingcut away or insulated beneath them at this point.

The projections-or teeth 6 of the breakwheel, which operate to open andclose the circuitcontrolled by it in the usual manner, -are wide enoughto be touched by adjacent pairs 70 m and it" m of the springs, and whenthewheel begins to rotate in the direction.

of the arrow, Fig. 2, it will first pass from beneath the spring 7c,thus leaving the side 4 of the main circuit open during the firsthalf-rotation of the said break-wheel, in which the notched surfacepasses beneathv the springs k on, each wide projection of said surfaceconnecting said springs, and thus connecting the side 3 of the maincircuitwith the ground through the spring m, and each notch of thebreak-wheel opening such groundcircuit in the well-known manner, andthus producinga number of operations of the receiving-instruments R,dependent on the arrangement of the teeth and notches in the break-wheelb, in the usual manner. During the first half-rotation thebreak-wheelrwill thus pass under the springs 70 m, and in the nexthalf-rotation it will co-operate with the springs 7a m, and thus closeand break a ground-circuit from the transmitter. to the portion 4 of themain line, including the receiving-instrument R at the main station. Aportion of the part of the breakwheel that co-operates with the groundedsprings m m is cut away, as shown at b Fig. 2, so that during acorresponding portion of the rotation of the said break-wheel thesprings 7c and and 70 are connected with the break-wheel, but the latteris not connected with the ground through the Springs on and m, andconsequently, after the signal has been transmitted through the side 3of the main line by the notched part, b of the break-wheel, the saidside v3 is retained in connection with the break-wheel, which no,longer, however, itself effects the said circuit, and in like mannerthe side 4 of the main circuit is retained in connection with thebreak-wheel for a certain period afterthe signal of said break-wheel hasbeen transmitted over the portion 4; of the main line. This connectionofthe break-wheel with the main line is for the purpose of transmittingthe local signal, as will now be explained.

ITO

X cuit will now be explained.

[5, the next pair.

5 ground at 12.

The teeth or notches of the break-wheel by which its signals aretransmitted only occupy a portion of its periphery, so as to give timefor the transmission of a local signal after 5 the main signal, and bythe same movement of the break-wheel shaft.

The relation of the local signaling instrument or drum eand itsco-operating springs f f &:c., to the break-wheel and main cir- The saidpairs of springs are connected in series with one another, as shown, onespring of one pairbeing in this instance made of the same piece of sheetmetal with the adjacent spring of The two springs of each pair are alsonormally connected togetherby loops 6 7 8, (see Fig. 5,) extending todifferent parts of the general locality indicated by the signal of themain break-wheel. For example,

zo-if the main break-wheel indicatesa given block or building in thecity, the loops 6 7 8 may represent different floors of the saidbuilding or different buildings of the said block or group of buildings.

The local circuit that controls the operation of transmitting devicecontains a battery B one pole of which is connected, as shown at 20,with one terminal of the magnet 'L', that operates the detent for thedrum, the other terminal of which is connected, as shown at 21, with onespring of the pair that is operated by the long strip only of the drum,from which the said local circuit is continued through the loop 6 to theother spring of said 3 5 pair, and thence the local circuit passesdirectly to one spring of the next pair and through the loop 7 to thenext spring thereof, and so on to the last spring of the last pair,which is connected, as shown at 9, with one 40 terminal of the magnetcl, that controls the detent for the break-wheel b, the other terminalof which magnet is connected, as shown at 10, with a switch or, whichnormally rests in contact with a piece connected with the The otherterminal of the battery B is connected by wire 13 with another switch a,which also normally rests against a contact-piece connected with theground at 12. The connections 13 and 20, between the battery 13' and themagnet z" and switch a,

respectively, are short and may be wires that are wholly inclosed withinthe casing that contains the transmitting instrument and battery, andthe magnet d is thus practically interposed between the extreme end ofthe local circuit, beginning at 20,'and the ground, so that a groundconnection coming upon the said local circuit anywhere outside of theshort wires 20 and 18 would short-circuit the magnet d, and consequentlysuch a groundnet t" would remain in the grounded circuit.

The loops 6 7 S normally close the connections between the pairs ofsprings ff, &c., so

that the strips e e &c., on the drum 0 would produce no material effectupon the current in the local circuit, so long as the loops 6 7 8 are intheir normally-closed condition. The said loops each contain one or morecircuitbreakers, which may be of any suitable or usual kind, the openingof any one of which causes the whole apparatus to operate as itdemagnetizes both magnets d 11 and releases the detent both of thebreak-wheel Z) and drum, so that both will rotate, as before described,until the motor 0 runs down.

A suitable form of thermostatic circuitbreaker to be used for fire-alarmpurposes is shown in Fig. 7, the same consisting of aconducting-reservoir made in two parts normally fastened together byeasily fusible solder, and said reservoir containing a volatile fluidwhich expands when the device is heated, and thus forcibly throws thetwo parts of the reservoir asunder when the easily-fusible solder issufficiently softened by the rise in temperature. The local circuit isconnected with the said separable parts of the reservoir, and is thusruptured when the said parts are separated, as just described. hen oneof the loops, as 6, is thus broken, the circuit between thecorresponding pair of springs f is opened, except when theconducting-stri p on the drum passes beneath them, so that saidconducting-strip will produce a momentary closure of the local circuit,and the number of strips that co-operate with the springs between whichthe circuit-loop is broken thus determines the character of the signal.Thus if loop No. 6 is broken, there will be one such closure, if loopNo. 7 two such closures, and so on, and if more than one loop is brokenthe signal consisting of the largest number of closures will betransmitted. The conducting-strips are arranged on the drum in suchposition that they co-operate with. the springs during the part of therotation in which the ground-spring m or m of the main break-wheel isover the cut-away portion of said main wheel, and such closures of thelocal circuit are caused to transmit signals in the main circuit, asfollows: The armature-lever i of the magnet 01 is connected, as shown at15, with a spring I), that makes contact withthe hub 19 of the wheel 1),except when the latter is held in its normal position by its detent, aswill be readily understood from Fig. 2. The front stop 1' for saidarmature lever is connected with the ground, so that as the saidarmature-lever responds to the closures in the local circuit it willcause a ground connection to be made through the break-wheel Z) to thespring 7c and portion 3 of the main circuit during one-half of therotation of said break-wheel, and to the spring 73' and port-ion 4 cfthe main circuit during the other half-rotation. The magnet 'i is thus arelay operated by the local circuit and itself operating the maincircuit.

The strips on the local signaling-drum are duplicated at opposite sides,as shown in Fi lIO 3, so as to operate in both parts of the rotation ofthe main break-wheel, and thus transmit the local signal to bothreceiving-instruments at the main oflicc if the main circuit is inworking condition. I

In order to prevent the possibility of a ground connection at some pointon the local circuit between the battery and magnet 2" on one side andthe break by which the local circuit is operated on the other side frommaking a circuit for the magnet t, and thus preventing it fromresponding to the breaks and closures of the local circuit producedby'the drum,the shaft 1) is provided with a cam t, which immediatelyafter the shaft is released operates the switches "n n, separating themfrom the ground connection 12 and moving them into contact with aconnecting-piece n which thus completes the local circuit, so that aground connection at any'other point on the local circuit would notaffect its operation.

The operation of the devices thus far described may be briefiy stated asfollows: The parts being normally in the condition represented in thediagram, if the current in the local circuit should weaken so as toendanger failure in case the apparatus were to be ops erated, or if aground connection should come on the said local circuit the magnet dwould release its armature and permit the break-wheel Z) to be operated;but the magnet t would still hold its armature and thus keep the detentin a posit-ion to prevent movement of the drum. The break-wheel I) wouldthus be permitted to make one or more complete rotations, according tothe construction of the engaging devices g g, and would then bearrested, and consequently the main signal, characteristic of thetransmitting device and entire locality protected by the local circuitsthereof, would be transmitted, but would not be followed by any localsignal, and information would thus be given at the main office thatsomething was wrong with the local circuit or apparatus, as the mainsignal, unaccompanied by the local signal, could only be produced inthis manner. If, on the other hand, one of the loops (3, 7, or 8 of thelocal circuit were opened, both the detents wouldbe released and thebreak-wheel I) would first make one or more rotations, sending in themain signal alone; but as soon as 'the device gg should become properlyengaged the drum 6 would move with the break-wheel and the instrumentwould then transmit the main signal, followed by the local signal, whichwould indicate that a fire had broken out and would designate not onlythe general locality, but that particular part of the general localitywhich was occupied by the loop that had been broken. There is apossibility that both detents might be released without any of the loops6 '7 8 being brokenas, for example, by the breaking of the circuitsoutside of said loops-and it might be desirable to indicate at the mainoffice that the drum had moved, even although the drum did not send anyparticular signal. Such an occurrence would be known by the fact thatthe main signal would be repeated a greater number of times than itwould if the detent of the break-wheel only were disengaged; but, as afurther means of distinguishing, the drum is provided with an additionalsignaling device with the ground, as shown in the diagram,

and the latter connected by wire 16 with the spring b so that when thecontact 7" passes over the springs r r immediately after the projectionsof the break-wheel have passed the spring 70 or k on one or the otherside of the main line will be connected with the ground, and the contact7' is made longer in the direction of rotation than the contacts of thebreak wheel or drum, so as to produce a dash, which distinguishes itfrom the dot-sig- 9o nal of the main break wheel and drum, and alsoserves to separate the main from the local signal, so as to avoidconfusion in reading the signals.

It is apparent that if the main break-Wheel detent had been released byderangement of the local circuit, such as before stated, the apparatuswould still remain in proper condition to produce the main and localsignals if one of the local circuit-loops should be broken, zoo

and when the apparatus is used as an automatic fire-alarm apparatus thereception of the main signal alone will callforan inspector to see whathas happened to the local circuit and to repair the same and settheapparatus in its original condition; but the main signal accompanied bythe local signal will be an swered by sending the proper means forextinguishing the fire.

I claim 1. The combination of a main circuit connecting signaltransmitting and receiving stations with a transmitting instrumentcomprising a main break-wheel controlling said IIO main circuits and alocal circuit and series of I 15 distinct signaling-surfaces orbreak-wheels connected to move simultaneously, the co-operatiug membersof which are permanently connected in series with one another in saidlocal circuit, and a motor for actuating the said main break-wheel and aseries of local circuit break-wheels, and a detent for said motorcontrolled by the said local circuit, substantially as described.

'2. The combination'of the motor and main 12 5 break-wheel connectedtherewith with a set of connected break-wheels or signaling-surfaces andengaging projections between said main break-wheel and set ofconnectedbreakwheels, and independent detents for said main breakwheelsand set of connected breakwheels, respectively, substantially as and forthe purpose described.

3. The combination of the main circuit connecting signal transmittingand receiving stations with a transmitting-instruinent com prising amain break-wheel controlling said main circuit, and a set of connectedbreakwheels or signaling-surfaces, and a local circuit controlledthereby and engaging projections between said main break-wheel and setof connected break-wheels, and independent detents for the said mainbreak-wheel and set of connected break-Wheels, and electro-magnetscontrolling said detents included in said local circuit, substantiallyas described.

t. The combination of the main circuit counecting signal transmittingand receiving stations with a transmitting-instrument comprising a mainbreak-wheel controlling said main circuit, and a set of connectedbreakwheels or signalingsurfaces, and a local circuit controlled therebyand engaging projections between said main break-wheel and set ofconnected break-wheels, and independent detents for the said mainbreak-wheel and set of connected break-wheels, and electro-magnetscontrolling said detents included in said local circuit, the armature ofthe magnet controlling the main dctent being adjusted to operate upon asmaller change in the current strength than that required for operatingthe magnet cont-rolling the detent for the set of connectedbreak-wheels, substantially as described.

5. The combination of the main circuit connecting signal transmittingand receiving stations with a transmitting-instrumcnt comprising a mainbreak-wheel controlling said main circuit, and a set of connectedbreakwheels or signaling-surfaces, and a local circuit controlledthereby an d engaging projections between said main break-wheel and setof connected break-wheels, and independent detents for the said mainbreak-wheel and set of connected break-Wheels, and electronlagnetscontrolling said detents included in said local circuit, the armature ofthe magnet that controls the detent for the set of con nectedbreak-wheels being connected with the main circuit, as set forth,whereby signals or changes in the local circuit produce correspondingsignals or changes in the main circuit, substantially as described.

6. The combination of the main circuit con necting signal transmittingand receiving stations with a transmitting-instru1nent comprising a mainbreak-wheel controlling said main circuit, and a set ofconnecting-wheels or signaling-surfaces, and a local circuit controlledthereby and engaging projections between said main break-wheel and setof connected break -wheels, and independent detents for the mainbreak-wheel and set of connected break wheels, and electro-magnetscontrolling said detents included in said local circuit, the said local.circuit having its terminals normally connected with the ground andincluding a battery placed near one of said grounded terminals, themagnet controlling the main break-wheel detent being placed near theother grounded terminal with substantially the whole local circuits andinstruments therein between it and the battery, substantially as and forthe purpose described.

7. The combination of the main circuit connecting signal transmittingand receiving stations with atransmitting-instrument comprising a mainbreak-wheel controlling said main circuit, and a set of connected wheelsor signalin surfaces and a local circuit controlled thereby and engagingprojections between said main break-wheel and set of connected break-W11eels and independent deten ts for the main break-wheels, and set ofconnccted break-wheels, and electro-magnets controlling said detentsincluded in said local circuit, the said local circuit having itsterminals normally connected with the ground and including a batteryplaced near one of said grounded terminals, the magnet controlling themain break-Wheel detent being placed near the other grounded terminalwith substantially the whole local circuits and instruments thereinbetween it and the battery, and a switch by which the terminals of thelocal circuit are disconnected from the ground and connected togetherwhen the break-wheel is set in operation, substantially as descr bed,

8. The combination of the main circuit connecting signal transmittingand receiving stations with a transmitting-instrument comprising themain break-wheel controlling said main circuit, and a set of connectedbreak- Wheels the co-operating members of which are connected byportions of a local circuit extending to different localities andincluding circuit-breakers, said local circuit being electricallydisconnected from the said main. circuit, but controlling and governingthe devices that operate to produce signals in said main circuit,substantially as and for the purpose described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

MORRIS MARTIN.

W itnesses:

Jos. P. L'rvnnnonn, JAS. J. MALoNnY.

l-lO

